My preferred German stuff back in the day:
1) Loader and tools for the Turbotape hardware mod by the Chaotic Hacker ... that setup saved soooo much time (600 B/s default, modded XC12 with software up to 6000 B/s).
2) Atmas II Macro-Assembler by Peter Finzel - lightning fast and very comfortable
3) S.A.M. program package by Harald Binner (published in German mag Atarimagazin, not the speech synthie by Tronix) - in particular the graphics editor/painting program blew my mind, full DLI support and pulldown menu driven!
4) Music utility Softsynth (published in German mag Happy Computer) - just wow at its time!
5) Bibosoft sector copier